Orange

Encyclopaedia entry

Interestingly, the orange shares the same entry as the pear, likely because it mentions both:

What was the fruit like? Unfortunately, no one can describe
a taste. All I can say is that, compared with those fruits,
the freshest grapefruit you've ever eaten was dull, and the
juiciest orange was dry, and the most melting pear was hard
and woody, and the sweetest wild strawberry was sour. And
there were no seeds or stones, and no wasps. If you had once
eaten that fruit, all the nicest things in this world would
taste like medicines after it. But I can't describe it. You
can't find out what it is like unless you can get to that
country and taste it for yourself.